1. Field of the Invention
The present invention relates to a light emitting diode and a method of fabricating the same, and more particularly, to a light emitting diode fabricated through a laser lift-off (LLO) process and a method of fabricating the same.
2. Discussion of the Background
Typically, a light emitting diode (LED) is formed by growing a GaN-based material on a substrate formed of GaN, sapphire, silicon, silicon nitride, and the like to emit light. In the LED with this structure, light is emitted from a light emitting layer located at an upper portion of the LED, travels above and below the light emitting layer, and is finally emitted from the LED through reflection, scattering, and refraction. To increase luminescence efficiency through refraction and reflection of light traveling above and below the light emitting layer, it is necessary to form a roughness on an upper side of the light emitting layer or to provide a reflection plate having good reflectivity to a lower side of the light emitting layer.
However, an upper side P-type layer of the light emitting layer is so thin that the roughness cannot be formed thereon or, if any roughness is formed thereon, provides an insignificant effect. Further, even when a metallic material having good reflectivity is deposited under the sapphire substrate located below the light emitting layer, some light is inevitably absorbed and disappears in the sapphire substrate. As such, when light is emitted from the lower part of the LED, it passes through the substrate where the light undergoes a significant loss. To reduce such a loss, a Si substrate or a metal substrate is provided to the LED for preventing absorption of light in the substrate while improving reflectivity, instead of using a sacrificial substrate, which has conventionally been used to grow semiconductor layers for use in the formation of the roughness or in the deposition of metal having high reflectivity to the substrate.
When using heterogeneous substrates instead of the sacrificial substrate, it is necessary to form an intermediate layer to bond the heterogeneous substrates to each other through application of heat and pressure from above and below the intermediate layer. During the application of heat and pressure, the heterogeneous substrates undergo deformation due to a difference in thermal expansion coefficient therebetween. Such deformation causes problems relating to characteristics and yield of subsequent processes.